RE: rotated grids

• To: galeon@xxxxxxxxxxxxxxxx
• Subject: RE: rotated grids
• From: stefano nativi <nativi@xxxxxxxxxxx>
• Date: Sat, 25 Jun 2005 10:46:46 +0200

---Stefano

-----Original Message-----
From: owner-galeon@xxxxxxxxxxxxxxxx
[mailto:owner-galeon@xxxxxxxxxxxxxxxx] On Behalf Of Rob Cermak
Sent: 23 June 2005 18:11
To: Norman Barker
Cc: John Caron; galeon@xxxxxxxxxxxxxxxx
Subject: rotated grids / RE: redo striped.nc

I am pleased that this has raised this question of Gaussian grids!  We
have rectified the grid in X-Y for our datasets, but we have abused the
describeCoverage XML to explain the Z dimension as follows

And, not sure if this is the same issue, rotated grids?
Grids like #203
and also RUC2 grid #252.  No where near monotonic for lat and
lon and typically the only georeference information given is
a reference lat/lon
and reference lon as below:
  lat1: 16.281
  lon1: 233.862
  lov: 265.000

RUC2 #252:
rec 1:0:date 2005062312 VGRD kpds5=34 kpds6=105 kpds7=10
levels=(0,10)
grid=252 10 m above gnd anl:
  VGRD=v wind [m/s]
  timerange 0 P1 0 P2 0 TimeU 1  nx 301 ny 225 GDS grid 3
num_in_ave 0 missing 0
  center 7 subcenter 0 process 105 Table 2
  Lambert Conf: Lat1 16.281000 Lon1 233.862000 Lov 265.000000
      Latin1 25.000000 Latin2 25.000000 LatSP 0.000000 LonSP 0.000000
      North Pole (301 x 225) Dx 20.318000 Dy 20.318000 scan 64 mode 8
  min/max data -12.4 12.2  num bits 8  BDS_Ref -124  DecScale
1 BinScale 0

Regridding is fine, but the preference is to maintain the
integrity of the data in its original form.

<RangeSet>
        <description>0.09999999403953552 0.19999998807907104
0.30000001192092896 0.5 0.699999988079071 1.0 2.0 3.0 5.0 7.0 10.0
20.0 30.0 50.0 70.0 100.0 150.0 200.0 250.0 300.0 400.0 500.0 600.0
700.0 850.0 975.0 1000.0 </description>

        <name>bands</name>
        <label>Pressure (hPa units) Levels</label>
        <axisDescription>
          <AxisDescription>
            <name>bands</name>
            <label>Bands/Channels/Samples</label>
            <values>

              <singleValue>1</singleValue>
              <singleValue>2</singleValue>
              <singleValue>3</singleValue>
              <singleValue>4</singleValue>
              <singleValue>5</singleValue>
              <singleValue>6</singleValue>

So that when you use the kvp BANDS then the client by indexing into
the space-separated description list can calculate which physical
level this corresponds to.

This is not an ideal solution, and I welcome comments on how we can go
about changing this.  Rectifying the grid to evenly spaced means a
change to the original dataset (though it is necessary to make
geotiff).

Hopefully this will be something that we can push into the GML in
JPEG2000 coverage format.

Norman